The antimicrobial activity of the lanthionine-containing bacteriocin nisin is restricted towards certain gram positive organisms and is optimal at pH 5.0. The antimicrobial activity of nisin is enhanced when used in combination with a chelator such as EDTA. The activity of the nisin chelator compositions have been found to be significantly greater or optimal at a pH greater than 5.0. For example, it has been determined that the antimicrobial activity towards Staphylococcus aureus of a nisin and EDTA composition is significantly greater at pH 8.0 than the activity of the same composition against S. aureus at pH 5.0 The combination of a chelator with nisin was also found to result in activity towards gram negative bacteria, an activity which is not inherent in nisin.
The present invention concerns lanthionine-containing bacteriocin compositions which are active in acidic pH below 5.0 and display considerable activity against gram negative bacteria. These low-pH-active compositions may be useful for example in methods of treating or preventing infections or growth of microorganisms in the gastrointestinal tract of humans and animals. These compositions when introduced into the gastrointestinal tract will act as bactericides even in the low-pH environment of the stomach. This antibacterial activity may be useful in containing the growth of infections caused by gastrointestinal pathogens such as species of Helicobacter, Escherichia, Salmonella, Bacillus, Clostridia, Bacteroides, Campylobacter and Yersinia. Such-low-pH active bacteriocin compositions would therefore be useful in the treatment of various diseases or symptoms due to the presence of such pathogenic bacteria.
Various gastrointestinal diseases or symptoms including diarrhea, gastritis, peptic and duodenal ulcer, and gastric carcinoma are due to the presence of pathogenic microorganisms in the gastrointestinal tract. Escherichia and Salmonella, in particular, but also certain species of Clostridia, Bacillus, Bacteroides, Campylobacter and Yersinia can be responsible for diarrhea especially in neonatal farm animals. (R.E. Holland, 1990, Clin. Microbiol. Rev. 3:345, "Some infectious causes of diarrhea in young farm animals.") Helicobacter pylori are implicated in gastritis, duodenal and peptic ulcer disease. (Peterson, W.L., 1991, New Eng. J. Med. 324: 1043, "Helicobacter pylori and peptic ulcer disease") and are also associated with gastric carcinoma. (Henderson, B.E., Ross, R.K., and Pike, M.C., 1991, Science 254:1131, "Toward the primary prevention of cancer," Nomura, A. Stemmermann, G.A., Chyou, P.H., Kato,I., Perez-Perez, G. and Blaser, M.J. (1991) New Eng. J. Med. 325: 1132 "Helicobacter pylori infection and gastric carcinoma among Japanese Americans in Hawaii."; Parsonnet, J., Friedman, G.D., Vandersteen, D.P., Chang, Y., Vogelman, J.H., Orentreich,N, and Sibley, R.K. (1991) New Eng. J. Med. 325:1127; Forman, D., Sitas, F., Newell, D.G., Stacey, A.R., Boreham, J., Peto, R., Campbell, T.C., Li, J. and Chen, J. (1990) Int. J. Cancer 46:608 "Geographic association of Helicobacter pylori antibody prevalence and gastric cancer mortality in rural China").
Many gastrointestinal pathogens are gram negative bacteria, organisms against which nisin would be expected to be inactive. (Hurst, A. , 1981, "Nisin," Adv. in App. Micr. V. 27 , p. 85-121. ) For example, Helicobacter pylori (which has also been identified in the prior art as Campylobacter pylori) is a gram negative microaerophilic bacillus that colonizes the gastric mucosa. Since 1983, when first reported in association with histologic gastritis, a relationship between suppression of H. pylori infection and improvement of gastric disorders has been noted. However, although numerous antibiotics have been tried against H. pylori infection, none have so far proved acceptable and no agent or regimen has been approved for use against this organism. Long term eradication of the organism has seldom been achieved and antibiotics themselves can produce unacceptable side effects. (Peterson, W.L., 1991, New Eng. J. Med. 324:1043 "Helicobacter pylori and peptic ulcer disease"; Warren, J.R., 1983, Lancet 1:1273, "Unidentified curved bacilli on gastric epithelium in active chronic gastritis"; Morgan et al., 1988, Gastroenterology 95:1178, "Nitrofurans in the treatment of gastritis associated with Campylobacter pylori"; Glupczynski, Y. et al., 1988, Am. J. Gastroenterol. 83:365 "Campylobacter pylori-associated gastritis: a double-blind placebo controlled trial with amoxycillin"; Rauws, E.A. et al., 1988, Gastroenterology 94:33, "Campylobacter pylori-associated chronic antral active gastritis"; Glupczynski, Y. 1990 in Helicobacter pylori, gastritis, and peptic ulcer"; Malfertheiner, P., Ditschuneit, H., Eds. Springer-Verlag, Berlin, Germany pp 49-58; Rauws, E.A. and Tytgat, G.N. 1990 Lancet 335:1233 "Cure of duodenal ulcer associated with eradication of Helicobacter pylori". O'Riordan, T. et al. , 1990, Gut 31:999 "Adjuvant antibiotic therapy in duodenal ulcers treated with colloidal bismuth subcitrate"; Weil, J. et al. , 1990, Aliment. Pharmacol. Ther., 4:651 "Helicobacter pylori infection treated with a tripotassium dicitrato bismuthate and metronidazole combination"; Coghlan, J.G., Gilligan, D., Humphries, H., et al., 1987, Lancet 2:1109 "Campylobacter pylori and recurrence of duodenal ulcer --a 12-month follow-up study"; Marshall, B.J. Goodwin, C.S., Warren, J.R. et al., 1988, Lancet 2:1437, "Prospective double-blind trial of duodenal ulcer relapse after eradication of Campylobacter pylori").
The present invention concerns pharmaceutical compositions comprising a lanthionine-containing bacteriocin such as nisin and a chelating agent with a suitable carrier for use in low-pH environments as bactericides. These compositions are stable and active at acidic pH and are useful for their antibacterial activity against gram negative bacteria in low-pH environments such as encountered in the gastrointestinal tract. Pharmaceutical nisin compositions according to the invention act quickly, so that when delivered into the stomach and gastrointestinal tract their activity should not be limited by the clearance rate of the stomach contents. Furthermore, unlike antibiotics, nisin compositions can be safely ingested. The pharmaceutical compositions may be used alone in treatment regimens or in combination with other pharmaceutical agents or drugs. The invention also concerns methods of using and making such compositions.